jeudi 22 décembre 2016

Humanity’s great leap into the space between the stars has, in a sense, already begun. NASA's Voyager 1 probe broke through the sun’s magnetic bubble to touch the interstellar wind. Voyager 2 isn’t far behind. New Horizons shot past Pluto on its way to encounters with more distant dwarf worlds, the rubble at the solar system’s edge.

Closer to home, we’re working on techniques to help us cross greater distances. Astronauts feast on romaine lettuce grown aboard the International Space Station, perhaps a preview of future banquets en route to Mars, or to deep space.

For the moment, sending humans to other stars remains firmly in the realm of science fiction—as in the new film, “Passengers,” when hibernating travelers awaken in midflight. But while NASA so far has proposed no new missions beyond our solar system, scientists and engineers are sketching out possible technologies that might one day help to get us there.

NASA’s Journey to Mars, a plan aimed at building on robotic missions to send humans to the red planet, could be helping lay the groundwork.

“Propulsion, power, life support, manufacturing, communication, navigation, robotics: the Journey to Mars is going to force us to make advances in every one of these areas,” said Jeffrey Sheehy, NASA’s Space Technology Missions Directorate chief engineer in Washington, D.C. “Those systems are not going to be advanced enough to do an interstellar mission. But Mars is stepping us that much farther into space. It’s a step along the way to the stars.”

Image above: A selfie taken by Curiosity the Mars rover in the Murray Buttes area. NASA’s Journey to Mars, a plan aimed at building on robotic missions to send humans to the red planet, could be helping lay the groundwork. Image Credits: NASA/JPL-Caltech/MSSS.

Charting the unknown

Hurling ourselves, Passengers-style, just to the nearest star, Proxima Centauri, would require crossing almost inconceivably vast distances. We would need truly exotic technology, such as suspended animation or multi-generational life support. That places in-person visits well out of reach, at least for the near term.

But the possibility of robotic interstellar probes is coming into much sharper focus. Space probe pioneers say the radiation, energy and particle-bathed space between the stars—the so-called interstellar medium—is itself a worthy science destination.

“We need more explorers, more of these local probes into this region, so we can understand better these interface conditions between our sun and the interstellar medium," said Leon Alkalai, an engineering fellow at NASA’s Jet Propulsion Laboratory in Pasadena, California, and co-author of a 2015 report on exploring interstellar space. "Like the ancient mariners, we want to start creating a map.”

Alkalai’s report, “Science and Enabling Technologies for the Exploration of the Interstellar Medium,” maps out the knowns and unknowns of largely uncharted regions, from the dark, distant, dwarf worlds of the Kuiper Belt to the “bow shock”—the turbulent transition thought to separate the sun’s bubble of plasma from the interstellar wind. Drawing on the work of more than 30 specialists during two workshops at the Keck Institute for Space Studies, the report poses pressing questions about the structure, composition and energy flow in this cosmic vastness. And it paints one of the most detailed pictures yet of a possible interstellar probe using present-day technology.

(Click on the image for enlarge)

Image above: An annotated illustration of the interstellar medium. The solar gravity lens marks the point where a conceptual spacecraft in interstellar space could use our sun as a gigantic lens, allowing zoomed-in close-ups of planets orbiting other stars. Image Credits: Charles Carter/Keck Institute for Space Studies.

Part of the report focuses on a “Design Reference Mission,” a conceptual starting point that allowed workshop scientists to begin teasing out some of the technical requirements of an interstellar probe. The resulting probe concept was meant to be “daring, challenging, inspirational to the public,” and “a rational first step towards attempting to reach another star,” the report said. It’s the latest in a long line of interstellar probe concepts by NASA scientists stretching back to the 1970s.

In this conceptual scenario, the disk-shaped probe in a bullet-shaped housing is launched as a payload on the Space Launch System, NASA’s next big rocket, in the late 2020s. With gravitational boosts from Earth, Jupiter and the sun itself, it could reach interstellar space in just 10 years. By comparison, it took Voyager 1 36 years to reach the heliopause, or the boundary of interstellar space.

The probe would rely on both rockets and electrical power from next-generation radioisotope thermoelectric generators, enhanced versions of the kind now onboard the Mars Curiosity Rover. Such a probe would carry a variety of sensors and a communications antenna. It could investigate the interstellar medium and its boundary with the solar system, and perhaps even conduct a flyby of a Kuiper Belt object, one of the many unknown space bodies that orbit the sun far beyond Pluto.

Future studies could examine the possibility of electric propulsion for the probe, or solar or electric sails.

Image above: Apollo 8, the first manned mission to the moon, entered lunar orbit on Christmas Eve, Dec. 24, 1968. That evening, the astronauts held a live broadcast from lunar orbit, in which they showed pictures of the Earth and moon as seen from their spacecraft. Possible future techonology like solar gravitational lensing may give us pictures of other worlds detailed enough to reveal continents and oceans, like this photo of Earth. Image Credit: NASA.

Solar gravity: a window on another world

One of the most extraordinary conceptual spacecraft detailed in the report also would exit the solar system, but only just. And its focus, literally, would be on alien worlds.

This conceptual spacecraft would be parked in near interstellar space to use our sun as a gigantic lens, allowing zoomed-in close-ups of planets orbiting other stars. A space telescope would be lofted to a position far beyond Pluto, some 550 times the distance from Earth to the sun, or farther. It would take advantage of an effect described by Einstein: the power of gravity to bend light rays.

The stream of light from a distant star and its planet would be bent around the edges of the sun, like water flowing around a rock, meeting on the other side at a focal point—where it would be greatly magnified. The telescope would be placed in just the right position to capture these images.

The images would be smeared into a ring around the sun, called an Einstein ring, and the technical challenges would be immense: the distortions would have to be corrected and the fragmentary images reassembled. But if successful, the lens could be powerful enough to reveal surface features of an exoplanet—a planet around another star.

“It would almost be like the Earthrise picture from the moon,” Alkalai said, recalling the iconic image sent back by the Apollo 8 astronauts in 1968. “You would see clouds and continents and oceans, that kind of scale of images. From Earth, every image of an exoplanet is a single pixel, so you’re looking with a straw at the exoplanet. If you want to image continents on an exoplanet, you need something like the solar gravitational lens.”

Once we are ready to take the giant stride to another star, the problem of propulsion takes center stage. Carrying bulky fuel tanks could increase the mass of an interstellar probe beyond the realm of feasibility.

But reaching even one-tenth the speed of light would allow a space probe to arrive at the nearest star in a 50-year time frame, Sheehy said.

“We would never be able to accelerate to that kind of velocity using a chemical reaction,” such as those in present-day rockets, he said.

One answer that might just possibly be within reach, he said, involves “beamed energy.” A powerful laser array, either on Earth’s surface or in orbit, could be used to accelerate space probes equipped with sails to some fraction of the speed of light. NASA’s Innovative Advanced Concepts Program (NIAC) recently chose one such project, led by Philip Lubin at the University of California, Santa Barbara, to receive a second grant for further development.

NIAC also recently provided funding for a conceptual project that might warm the hearts of “Passengers” fans. Called “Advanced Torpor Inducing Transfer Habitats for Human Stasis to Mars,” this research effort by John Bradford of Space Works Inc., in Atlanta, investigates how to place astronauts in a deep sleep state with reduced metabolic rates for trips between Earth and Mars. While it isn’t true suspended animation or intended for interstellar travel, such a project highlights the extreme technical difficulties involved in sending fragile human bodies across the reaches of interstellar space.

Image above: The first blooming zinnia flower in the Veggie plant growth system aboard the International Space Station. Growing food in space is one of the challenges humans will have to face before attempting interstellar travel. Image Credit: NASA.

Printing a pizza

If our species ever attempts such trips, they could take many decades or even centuries, perhaps requiring some kind of suspension and revival or vessels that can sustain human life for several generations.

“Maybe the people we launch won’t be the people who actually reach Alpha Centauri,” Sheehy said. “It will be their kids. But you’ve got to eat for those 80 years.”

Learning to grow food in space could help, he said, though growing plants from seeds requires “real estate in space. A tomato plant is so big, a head of lettuce is a certain size.”

Another possibility is using 3-D printers that “build 3-D objects up layer by layer. Why couldn’t we build a cell that way? Why couldn’t we build food that way? Could you print a pizza?”

“The notion of sending humans to interstellar space is so far out in the sense that people need to have resources on the scale of a planet,” he said. “The only sci-fi story that I like, that might have some scientific basis, is not to build a Star Trek Enterprise but to really hijack an asteroid.

“Imagine a population that would be able to be on a binary asteroid. Then they could use one of them to swing the other one into interstellar space. Then you have resources on the asteroid, a source of iron, carbon, other materials. They could mine that as a source of resources for living, for energy. You would have to imagine something like this designed for many, many generations.”

But the daunting challenges even to sending robotic probes to the stars should be motivating, not discouraging, Sheehy said.

“Anywhere we’ve ever gone as humans, we always learn something, even if it’s just over the next mountain range,” he said. “A lot of times you discover something about yourself on a journey like that. We always find something that surprises us.”

On a clear evening in April of 1789, the renowned astronomer William Herschel continued his unrelenting survey of the night sky, hunting for new cosmic objects — and found cause to celebrate! He spotted this bright spiral galaxy, named NGC 4707, lurking in the constellation of Canes Venatici or The Hunting Dog. NGC 4707 lies roughly 22 million light-years from Earth.

NGC stands for "New General Catalogue of Nebulae and Clusters of Stars."

Over two centuries later, the NASA/ESA Hubble Space Telescope is able to "chase down" and view the same galaxy in far greater detail than Herschel could, allowing us to appreciate the intricacies and characteristics of NGC 4707 as never before. This striking image comprises observations from Hubble’s Advanced Camera for Surveys (ACS), one of a handful of high-resolution instruments currently aboard the space telescope.

Herschel himself reportedly described NGC 4707 as a “small, stellar” galaxy; while it is classified as a spiral (type Sm), its overall shape, center, and spiral arms are very loose and undefined, and its central bulge is either very small or non-existent. It instead appears as a rough sprinkling of stars and bright flashes of blue on a dark canvas.

The blue smudges seen across the frame highlight regions of recent or ongoing star formation, with newborn stars glowing in bright, intense shades of cyan and turquoise.

This comparison of two views from NASA's Cassini spacecraft, taken fairly close together in time, illustrates a peculiar mystery: Why would clouds on Saturn's moon Titan be visible in some images, but not in others?

In the top view, a near-infrared image from Cassini's imaging cameras, the skies above Saturn's moon Titan look relatively cloud free. But in the bottom view, at longer infrared wavelengths, Cassini sees a large field of bright clouds. Even though these views were taken at different wavelengths, researchers would expect at least a hint of the clouds to show up in the upper image. Thus they have been trying to understand what's behind the difference.

As northern summer approaches on Titan, atmospheric models have predicted that clouds will become more common at high northern latitudes, similar to what was observed at high southern latitudes during Titan's late southern summer in 2004. Cassini's Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) teams have been observing Titan to document changes in weather patterns as the seasons change, and there is particular interest in following the onset of clouds in the north polar region where Titan's lakes and seas are concentrated.

Cassini's "T120" and "T121" flybys of Titan, on June 7 and July 25, 2016, respectively, provided views of high northern latitudes over extended time periods -- more than 24 hours during both flybys. Intriguingly, the ISS and VIMS observations appear strikingly different from each other. In the ISS observations (monochrome image at top), surface features are easily identifiable and only a few small, isolated clouds were detected. In contrast, the VIMS observations (color image at bottom) suggest widespread cloud cover during both flybys. The observations were made over the same time period, so differences in illumination geometry or changes in the clouds themselves are unlikely to be the cause for the apparent discrepancy: VIMS shows persistent atmospheric features over the entire observation period and ISS consistently detects surface features with just a few localized clouds.

The answer to what could be causing the discrepancy appears to lie with Titan's hazy atmosphere, which is much easier to see through at the longer infrared wavelengths that VIMS is sensitive to (up to 5 microns) than at the shorter, near-infrared wavelength used by ISS to image Titan's surface and lower atmosphere (0.94 microns). High, thin cirrus clouds that are optically thicker than the atmospheric haze at longer wavelengths, but optically thinner than the haze at the shorter wavelength of the ISS observations, could be detected by VIMS and simultaneously lost in the haze to ISS -- similar to trying to see a thin cloud layer on a hazy day on Earth. This phenomenon has not been seen again since July 2016, but Cassini has several more opportunities to observe Titan over the last months of the mission in 2017, and scientists will be watching to see if and how the weather changes.

These two images were taken as part of the T120 flyby on June 7 (VIMS) and 8 (ISS), 2016. The distance to Titan was about 28,000 miles (45,000 kilometers) for the VIMS image and about 398,000 miles (640,000 kilometers) for the ISS image. The VIMS image has been processed to enhance the visibility of the clouds; in this false-color view, clouds appear nearly white, atmospheric haze is pink, and surface areas would appear green.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado. The visual and infrared mapping spectrometer team is based at the University of Arizona.

Pandora Up Close

This image from NASA's Cassini spacecraft is one of the highest-resolution views ever taken of Saturn's moon Pandora. Pandora (52 miles, 84 kilometers) across orbits Saturn just outside the narrow F ring.

The spacecraft captured the image during its closest-ever flyby of Pandora on Dec. 18, 2016, during the third of its grazing passes by the outer edges of Saturn's main rings. (For Cassini's closest view prior to this flyby, see PIA07632, which is also in color.)

The image was taken in green light with the Cassini spacecraft narrow-angle camera at a distance of approximately 25,200 miles (40,500 kilometers) from Pandora. Image scale is 787 feet (240 meters) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colorado.

China launched its first minisatellite dedicated to the carbon dioxide detection and monitoring at 15:22 UTC on December 22 using a Long March-2D (Chang Zheng-2D) launch vehicle. Launch of TanSat occurred from the LC43/603 launch complex of the Jiuquan Satellite Launch Center.

TanSat spacecraft

The main objective of the TanSat mission is to retrieve the atmosphere column-averaged CO2 dry air mole fraction with precisions of 1% (4 ppm) on national and global scales. The scientific goal of the project is to improve the understanding on the global CO2 distribution and its contribution to the climate change, and also to monitor the CO2 variation on seasonal time scales.

(Highlights: Week of Dec. 12, 2016) - Crew members on the International Space Station installed a new device to help regulate temperature and an investigation created by aspiring scientists still in high school.

NASA astronaut Shane Kimbrough installed the Phase Change Heat Exchanger Project (Phase Change HX) to begin an investigation into ways to maintain safe temperatures in space. The lack of atmosphere or protection from the sun’s heat makes regulating temperature in space difficult. Phase-change material heat exchangers can help by freezing or thawing a material to maintain critical temperatures inside a spacecraft, protecting crew members and equipment. A wax-based exchanger has been used in the past, but this water-based version has significantly better energy storage and has not been tested in space. By using materials that can change phase from liquid to vapor, depending on the temperature, facilities can more easily move heat into areas that must be warmed by removing heat from areas that much be cooled. This new hardware introduces the capability by supplying sub-zero fluid temperatures to investigations that need them. These tests will improve the design of this style of exchanger on Earth, where it is used as a low-energy method to control temperatures in chemical plants and power plants.

Image above: The Japanese HTV-6 cargo vehicle is seen during final approach to the International Space Station before it is captured by the remote Canadarm 2. HTV-6 launched from the Tanegashima Space Center in southern Japan on Friday, Dec. 9, and arrived at the station on Tuesday, Dec. 13. The vehicle was loaded with more than 4.5 tons of supplies, water, spare parts and experiment hardware. Image Credit: NASA.

ESA (European Space Agency) astronaut Thomas Pesquet installed the NanoRacks-CUBERIDER-1 (NanoRacks-CR-1) module into one of the NanoRacks platforms – a shoebox-sized section of one of the larger racks that stores science experiments on the space station. This educational module runs a computer code written by high school students to conduct tests and record data about the microgravity environment. This particular investigation monitors for radiation and any movement on station using a small camera viewing the inside of the orbiting laboratory. The investigation is one of many ways the space station program engages students, encouraging studies in the science, technology engineering and math fields as future scientists devise their own experiments and experience space science first hand

Kimbrough installed nine radiation detectors throughout the Japanese Pressurized Module and Japanese Experiment Logistics Module as part of the Area Passive Dosimeter for Life-Science Experiments in Space (Area PADLES) investigation. The JAXA (Japan Aerospace Exploration Agency) dosimeters continuously monitor the radiation dose aboard the space station. Radiation exposure can have significant effects on living organisms, including the crew and biological investigations being done on the space station in the Japanese Experiment Module, Kibo. Measuring radiation in space is essential to protecting astronauts, developing monitors and shielding for life sciences experiments in space, and designing wall thicknesses for future space vehicles. On Earth, the dosimetry technique measures radiation doses for people working around high-energy accelerators -- used with high-speed microscopes to image cancer cells.

Image above: NASA astronaut Peggy Whitson performs an Optical Coherence Tomography (OCT) exam. Researchers believe that the measurement of visual, vascular and central nervous system changes over the course of this experiment and during the subsequent post-flight recovery will assist in the development of countermeasures, clinical monitoring strategies, and clinical practice guidelines. Image Credit: NASA.

Pesquet began four tests for the Aquaporin Inside Membrane Testing in Space (AquaMembrane) investigation which looks into a potential new method for water recovery on space vehicles. As one of the basic needs for survival, recovering water from moisture in the cabin atmosphere and filtering waste water –- sweat and urine -- for reuse is an important part of the station’s life support system. This ESA study collects and treats waste water in space that will be transported back to Earth for analysis. The investigation may lead to improved efficiency for reclaiming water in space, reducing the frequency for resupply from Earth and impact life support systems for future long-duration exploration missions beyond our orbit. The AquaMembrane is developed using a technology called forward osmosis, which is also being tested to desalinate ocean water for use on Earth.

JCSat-15, owned by SKY Perfect JSat, will offer a range of communications services for Japan, including broadcasting, data transfer, and maritime and aeronautical applications for the Oceania and Indian Ocean regions.

Both satellites are designed to last more than 15 years.

JCSat-15 satellite

The payload mass for this launch was 10 722 kg. The satellites totalled about 9833 kg, with payload adapters and carrying structures making up the rest.

Image above: The BASE experiment zone with the antiproton transfer line and the superconducting magnet. The screens show the signals from single antiprotons stored in the BASE measurement traps. (Image: Stefan Sellner/CERN).

The Baryon Antibaryon Symmetry Experiment (BASE) at the Antiproton Decelerator (AD) facility at CERN has managed to keep a bunch of antiprotons trapped in its reservoir for more than one year now. The shot of antiprotons – the antimatter companions of protons – was loaded into the experiment’s reservoir trap on 12 November 2015 and the collaboration is still working with the same particles. This sets a number of records: no-one has previously managed to keep antimatter trapped for such a long period and, to the best of our knowledge, no other charged particles have been consistently confined for this long.

The BASE experiment is devoted to the precise comparison of the properties of protons and antiprotons: any discrepancy detected would hint at new physics beyond the Standard Model.

BASE conducts its high-precision experiments on one antiproton at a time, so it does not need a continuous beam of antiprotons. One shot of antiprotons from the AD facility contains enough antiprotons for the needs of BASE. “The antiproton reservoir enables us to run autonomously for months, which is especially useful in the winter shutdown period when there is no beam available from the AD,” says Stefan Ulmer, spokesperson for the BASE collaboration.

The reservoir trap is inside a cylinder with a volume of 1.2 litres. The particles are trapped by two overlying magnetic and electric fields, which keep the particles in a small volume in the centre of the trap. On one side of the trap there is a metal window, thin enough to allow the antiprotons to pass through but strong enough to ensure complete insulation from the outside. All the other sides of the trap are made from solid copper. The cylinder is then cooled to about 6 K (-267 °C) with liquid helium, so that an almost perfect vacuum is created. Indeed, if an antiproton meets a matter particle, it will be annihilated and disappear. The BASE team must therefore ensure that there are virtually no residual gas particles left in the reservoir. “Given that we have not observed any antiproton disappearance yet,” says Christian Smorra, a research fellow on the BASE collaboration, “we can say that there are less than three matter particles left per cubic centimetre.”

BASE’s reservoir trap has another unique characteristic. Antiparticles are the rarest species of particles in our universe, as they are only created in high-energy particle collisions or in a nuclear decay. Proton–antiproton symmetry is always extremely unbalanced towards protons. A reservoir of hundreds of antiprotons all confined in a small space in an almost perfect vacuum represents a significant local inversion of this asymmetry. “What is unique about BASE is that we can trap the particles for as long as we want to,” says Stefan Sellner, a post-doc researcher at BASE. “Also, our antiprotons are the coldest antimatter particles ever prepared, at temperatures very close to absolute zero,” he remarks.

At the end of the year, the BASE experiment will undergo a period of machine maintenance and development, which means that the antiprotons will be freed from the reservoir trap in which they have cohabited for over a year.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

New receivers improve ALMA’s ability to search for water in the Universe

The merging galaxy system Arp 220 from ALMA and Hubble

The Atacama Large Millimeter/submillimeter Array (ALMA) in Chile has begun observing in a new range of the electromagnetic spectrum. This has been made possible thanks to new receivers installed at the telescope’s antennas, which can detect radio waves with wavelengths from 1.4 to 1.8 millimetres — a range previously untapped by ALMA. This upgrade allows astronomers to detect faint signals of water in the nearby Universe.

ALMA observes radio waves from the Universe, at the low-energy end of the electromagnetic spectrum. With the newly installed Band 5 receivers, ALMA has now opened its eyes to a whole new section of this radio spectrum, creating exciting new observational possibilities.

The European ALMA Programme Scientist, Leonardo Testi, explains the significance: “The new receivers will make it much easier to detect water, a prerequisite for life as we know it, in our Solar System and in more distant regions of our galaxy and beyond. They will also allow ALMA to search for ionised carbon in the primordial Universe.”

Band 5 ALMA receiver

It is ALMA’s unique location, 5000 metres up on the barren Chajnantor plateau in Chile, that makes such an observation possible in the first place. As water is also present in Earth’s atmosphere, observatories in less elevated and less arid environments have much more difficulty identifying the origin of the emission coming from space. ALMA’s great sensitivity and high angular resolution mean that even faint signals of water in the local Universe can now be imaged at this wavelength [1].

The Band 5 receiver, which was developed by the Group for Advanced Receiver Development (GARD) at Onsala Space Observatory, Chalmers University of Technology, Sweden, has already been tested at the APEX telescope in the SEPIA instrument. These observations were also vital to help select suitable targets for the first receiver tests with ALMA.

The first production receivers were built and delivered to ALMA in the first half of 2015 by a consortium consisting of the Netherlands Research School for Astronomy (NOVA) and GARD in partnership with the National Radio Astronomy Observatory (NRAO), which contributed the local oscillator to the project. The receivers are now installed and being prepared for use by the community of astronomers.

One of the Band 5 receivers for ALMA

To test the newly installed receivers observations were made of several objects including the colliding galaxies Arp 220, a massive region of star formation close to the centre of the Milky Way, and also a dusty red supergiant star approaching the supernova explosion that will end its life [2].

To process the data and check its quality, astronomers, along with technical specialists from ESO and the European ALMA Regional Centre (ARC) network, gathered at the Onsala Space Observatory in Sweden, for a "Band 5 Busy Week" hosted by the Nordic ARC node [3]. The final results have just been made freely available to the astronomical community worldwide.

Team member Robert Laing at ESO is optimistic about the prospects for ALMA Band 5 observations: “It's very exciting to see these first results from ALMA Band 5 using a limited set of antennas. In the future, the high sensitivity and angular resolution of the full ALMA array will allow us to make detailed studies of water in a wide range of objects including forming and evolved stars, the interstellar medium and regions close to supermassive black holes.”

One of the Band 5 receivers for ALMA

Notes:

[1] A key spectral signature of water lies in this expanded range — at a wavelength of 1.64 millimetres.

[2] The observations were performed and made possible by the ALMA Extension of Capabilities team in Chile.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

mardi 20 décembre 2016

Capri Chasma is located in the eastern portion of the Valles Marineris canyon system on Mars, the largest known canyon system in the Solar System. Deeply incised canyons such as this are excellent targets for studying the Martian crust, as the walls may reveal many distinct types of bedrock.

This section of the canyon was targeted by HiRISE based on a previous spectral detection of hematite-rich deposits in the area. Hematite, a common iron-oxide mineral, was first identified here by the Mars Global Surveyor Thermal Emission Spectrometer (TES). In this TES image, red pixels indicate higher abundances of hematite, while the blue and green pixels represent different types of volcanic rocks (e.g., basalt).

Hematite in the Meridiani Planum region was also detected with the TES instrument (which we can see with the bright red spot on the Global TES mineral map). As a consequence, Meridiani Planum was the first landing site selected on Mars due to the spectral detection of a mineral that may have formed in the presence of liquid water.

Shortly after landing, the Opportunity rover detected the presence of hematite in the form of concretions called "blueberries." The blueberries are found in association with layers of sulfate salt-rich rocks. The salts are hypothesized to have formed through the raising and lowering of the groundwater table. During one such an event, the rock altered to form the hematite-rich blueberries. As the rock was eroded away, the more resistant hematite-rich blueberries were plucked out and concentrated on the plains as a "lag" deposit. Martian blueberries are observed to be scattered across the plains of Meridiani along Opportunity's traverse from Eagle Crater to Endeavor Crater, where Opportunity continues to explore after its mission began over 10 years ago.

This infrared-color image close-up highlights what is possibly the hematite-rich deposits nestled between different types of bedrock terraces in Capri Chasma. The bluish terrace is likely volcanic in origin, possibly basaltic, whereas the greenish rocks remain unidentified.

The central reddish terrace is possibly where some of the hematite may be concentrated. The higher elevation terrace with the lighter-colored materials is likely a sulfate-rich rock (based on CRISM data in the area). Given the presence of both sulfate salts and hematite in this area, akin to the deposits and associations explored by the Opportunity rover in Meridiani Planum, it might be that these materials in Capri Chasma may share a similar origin.

Mars Reconnaissance Orbiter (MRO). Image Credits: NASA/JPL-Caltech

The yellow rectangular box shown on the TES spectral map outlines the corresponding location of the HiRISE image. Although the outline does not appear to contain a high hematite abundance, we note that the lower resolution of TES (about 3 to 6 kilometers per pixel) may exclude smaller exposures and finer sub-pixel details not-yet captured, but could be with HiRISE. A follow-up observation by the CRISM spectrometer may reveal additional details and a spectral signature for hematite in the vicinity at a finer resolution than TES.

A new study using a NASA satellite instrument orbiting Earth has found that small, environmental changes in polar food webs significantly influence the boom-and-bust, or peak and decline, cycles of phytoplankton. These findings will supply important data for ecosystem management, commercial fisheries and our understanding of the interactions between Earth’s climate and key ocean ecosystems.

“It’s really important for us to understand what controls these boom-and-bust cycles, and how they might change in the future so we can better evaluate the implications on all other parts of the food web,” said Michael Behrenfeld, a marine plankton expert at Oregon State University in Corvallis.

Phytoplankton also influence Earth’s carbon cycle. Through photosynthesis, they absorb a great deal of the carbon dioxide dissolved in the upper ocean and produce oxygen, which is vital for life on Earth. This reduces the amount of carbon dioxide in the atmosphere.

Behrenfeld, along with scientists from NASA’s Langley Research Center in Hampton, Virginia, and several other institutions collaborated on the study. The findings were published Monday in Nature Geoscience.

Coastal economies and wildlife depend on what happens to tiny green plants, or phytoplankton, at the base of the ocean food chain. Commercial fisheries, marine mammals and birds all depend on phytoplankton blooms. The new study shows that accelerations in growth rate cause blooms by allowing phytoplankton to outgrow the animals that prey on them. When this happens, the phytoplankton populations rapidly increase.

However, as soon as that acceleration in growth stops, the predatory animals catch up by eating the ocean plants and the bloom ends. This new understanding goes against traditional theories that blooms only occur when phytoplankton growth rates exceed a specific threshold of fast growth and that they end when these growth rates fall below that threshold again.

Behrenfeld compares the new idea to two rubber balls connected by a rubber band.

“A green ball represents the phytoplankton. A red one represents all the things that eat or kill the phytoplankton,” he said. “Take the green ball and whack it with a paddle. As long as that green ball accelerates, the rubber band will stretch and the red ball won’t catch the green ball. As soon as the green ball stops accelerating, the tension in the rubber band will pull that red ball up to it and the red ball will catch the green ball.”

NASA’s Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP), an instrument aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite launched in 2006, uses a laser to take measurements. Scientists used the instrument to continuously monitor plankton in polar regions from 2006 to 2015.

“CALIOP was a game-changer in our thinking about ocean remote sensing from space,” said Chris Hostetler, a research scientist at Langley. “We were able to study the workings of the high-latitude ocean ecosystem during times of year when we were previously completely blind.”

Ocean ecosystems typically are monitored with satellite sensors that simply measure sunlight reflected back to space from the ocean. These instruments have a problem seeing the ocean plankton in polar regions because of limited sunlight and persistent clouds that obscure their view of the ocean surface. The lidar shines its own light – a laser – and can illuminate and measure the plankton day or night, in between clouds, and even through some clouds.

The study also reveals that year-to-year variations in this constant push and pull between predator and prey have been the primary driver of change in Arctic plankton stocks over the past decade. In the Southern Ocean around Antarctica, though, changes in the ice cover were more important to phytoplankton population fluctuations than were differences in growth rates and predation.

“The take home message is that if we want to understand the biological food web and production of the polar systems as a whole, we have to focus both on changes in ice cover and changes in the ecosystems that regulate this delicate balance between predators and prey,” said Behrenfeld.

The current CALIOP lidar was engineered to take atmospheric measurements, not optimized for ocean measurements. Nonetheless, the CALIOP ocean measurements are scientifically valuable, as demonstrated by the results of this study.

New lidar technology is being tested that would allow scientists to better measure how phytoplankton are distributed through the sunlit layer of the ocean. This new capability will improve knowledge of phytoplankton concentrations and photosynthesis and will reveal more about the causes of phytoplankton blooms. This knowledge is critical for understanding cycling of ocean carbon, and for determining and managing the health of global ocean ecosystems.

The CALIPSO satellite mission is a collaboration between NASA and France’s space agency, the Centre National d’Etudes Spatiales. The University of Maine in Orono, the University of California, Santa Barbara, and Princeton University also participated in the study.

NASA’s work in Earth science is making a difference in people’s lives around the world every day. Scientists worldwide use NASA data to tackle some of the biggest questions about how our planet is changing now and how Earth could change in the future.

For more information about CALIPSO satellite and NASA's Earth science activities, visit:

Image above: The data used in this image were taken with Hubble’s Advanced Camera for Surveys in September 2015. Image Credits: NASA, ESA, STScI, K. Sandstrom (University of California, San Diego), and the SMIDGE team.

NASA’s Hubble Space Telescope captured two festive-looking nebulas, situated so as to appear as one. They reside in the Small Magellanic Cloud, a dwarf galaxy that is a satellite of our Milky Way galaxy. Intense radiation from the brilliant central stars is heating hydrogen in each of the nebulas, causing them to glow red.

The nebulas, together, are called NGC 248. They were discovered in 1834 by the astronomer Sir John Herschel. NGC 248 is about 60 light-years long and 20 light-years wide. It is among a number of glowing hydrogen nebulas in the dwarf satellite galaxy, which is located approximately 200,000 light-years away in the southern constellation Tucana.

The image is part of a study called Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE). Astronomers are using Hubble to probe the Milky Way satellite to understand how dust is different in galaxies that have a far lower supply of heavy elements needed to create dust. The Small Magellanic Cloud has between a fifth and a tenth of the amount of heavy elements that the Milky Way does. Because it is so close, astronomers can study its dust in great detail, and learn about what dust was like earlier in the history of the universe. “It is important for understanding the history of our own galaxy, too,” explained the study’s principal investigator, Dr. Karin Sandstrom of the University of California, San Diego. Most of the star formation happened earlier in the universe, at a time where there was a much lower percentage of heavy elements than there is now. “Dust is a really critical part of how a galaxy works, how it forms stars,” said Sandstrom.

Animation above: This sequence of three HiRISE images from NASA's Mars Reconnaissance Orbiter shows the growth of a branching network of troughs carved by thawing carbon dioxide over the span of three Martian years. This process may also form larger radially patterned channel features known as Martian "spiders." Animation Credits: NASA/JPL-Caltech/Univ. of Arizona.

Erosion-carved troughs that grow and branch during multiple Martian years may be infant versions of larger features known as Martian "spiders," which are radially patterned channels found only in the south polar region of Mars.

Researchers using NASA's Mars Reconnaissance Orbiter (MRO) report the first detection of cumulative growth, from one Martian spring to another, of channels resulting from the same thawing-carbon-dioxide process believed to form the spider-like features.

The spiders range in size from tens to hundreds of yards (or meters). Multiple channels typically converge at a central pit, resembling the legs and body of a spider. For the past decade, researchers have checked in vain with MRO's High Resolution Imaging Science Experiment (HiRISE) camera to see year-to-year changes in them.

"We have seen for the first time these smaller features that survive and extend from year to year, and this is how the larger spiders get started," said Ganna Portyankina of the University of Colorado, Boulder. "These are in sand-dune areas, so we don't know whether they will keep getting bigger or will disappear under moving sand."

Dunes appear to be a factor in how the baby spiders form, but they may also keep many from persisting through the centuries needed to become full-scale spiders. The amount of erosion needed to sculpt a typical spider, at the rate determined from observing active growth of these smaller troughs, would require more than a thousand Martian years. That is according to an estimate by Portyankina and co-authors in a recent paper in the journal Icarus. One Martian year lasts about 1.9 Earth years.

"Much of Mars looks like Utah if you stripped away all vegetation, but 'spiders' are a uniquely Martian landform," said Candice Hansen of the Planetary Science Institute, Tucson, Arizona, a co-author of the report.

Carbon-dioxide ice, better known as "dry ice," does not occur naturally on Earth. On Mars, sheets of it cover the ground during winter in areas near both poles, including the south-polar regions with spidery terrain. Dark fans appear in these areas each spring.

Images above: These five images from the HiRISE camera on NASA's Mars Reconnaissance Orbiter show different Martian features of progressively greater size and complexity, all thought to result from thawing of seasonal carbon dioxide ice that covers large areas near Mars' south pole during winter. Images Credits: NASA/JPL-Caltech/Univ. of Arizona.

Hugh Kieffer of the Space Science Institute in Boulder put those factors together in 2007 to deduce the process linking them: Spring sunshine penetrates the ice to warm the ground underneath, causing some carbon dioxide on the bottom of the sheet to thaw into gas. The trapped gas builds pressure until a crack forms in the ice sheet. Gas erupts out, and gas beneath the ice rushes toward the vent, picking up particles of sand and dust. This erodes the ground and also supplies the geyser with particles that fall back to the surface, downwind, and appear as the dark spring fans.

This explanation has been well accepted, but actually seeing a ground-erosion process that could eventually yield the spider shapes proved elusive. Six years ago, researchers using HiRISE reported small furrows appearing on sand dunes near Mars' north pole at sites where eruptions through dry ice had deposited spring fans. However, those furrows in the far north disappear within a year, apparently refilled with sand.

The newly reported troughs near the south pole are also at spring-fan sites. They have not only persisted and grown through three Mars years so far, but they also formed branches as they extended. The branching pattern resembles the spidery terrain.

"There are dunes where we see these dendritic [or branching] troughs in the south, but in this area, there is less sand than around the north pole," Portyankina said. "I think the sand is what jump starts the process of carving a channel in the ground."

Harder ground lies beneath the sand. Forming a spider may require ground soft enough to be carved, but not so loose that it refills the channels, as in the north. The new research sheds light on how carbon dioxide shapes Mars in unearthly ways.

Mars Reconnaissance Orbiter (MRO). Image Credits: NASA/JPL-Caltech

MRO began orbiting Mars in 2006. "The combination of very high-resolution imaging and the mission's longevity is enabling us to investigate active processes on Mars that produce detectable changes on time spans of seasons or years," said MRO Deputy Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, California. "We keep getting surprises about how dynamic Mars is."

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp. of Boulder. JPL, a division of Caltech in Pasadena, California, manages the MRO Project for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it. For additional information about the project, visit: http://mars.nasa.gov/mro

JAXA successfully launched the second Epsilon Launch Vehicle with Exploration of energization and Radiation in Geospace (ERG) aboard at 8:00 p.m. on December 20, 2016 (JST) from the Uchinoura Space Center. The launch vehicle flew as planned, and at approximately 13 minutes and 27 seconds after liftoff, the separation of ERG was confirmed.

Launch of ERG "ARASE" by Epsilon-2

The signals were received in the Santiago Ground Station, the Republic of Chile at 8:37 p.m. (JST). ERG's solar array paddles have been deployed as planned. Also, ERG has completed the attitude control based on the sun acquisition. The satellite is currently in good health. JAXA has nicknamed ERG "ARASE".

Energization and Radiation in Geospace (ERG) satellite

Japan’s Epsilon rocket launches JAXA’s Exploration of Energization and Radiation in Geospace (ERG) satellite to investigate the Van Allen radiation belts and study the origins of geomagnetic storms. This launch is the second flight of Japan’s small Epsilon launch vehicle.

JAXA has nicknamed ERG "ARASE" for the following reasons:

- ERG starts a new journey to Van Allen radiation belts, located in the Earth's inner magnetosphere, where energetic charged particles are trapped. "ARASE", a Japanese word for a river raging with rough white water is a fitting description for the journey that lies ahead of ERG.

- After Arase River, which runs Kimotsuki, Kagoshima, where JAXA's Uchinoura Space Center is located. Arase River has a local folktale of bird's beautiful singing. Since ERG observes "chorus" *, it conveys the significance well.

* Chorus is a plasma wave generated in the magnetic equator of Earth's magnetosphere. Its frequency band ranges within several kHz. Audibly converted, Chorus sounds much like bird's singing.

lundi 19 décembre 2016

Although there are no seasons in space, this cosmic vista invokes thoughts of a frosty winter landscape. It is, in fact, a region called NGC 6357 where radiation from hot, young stars is energizing the cooler gas in the cloud that surrounds them.

This composite image contains X-ray data from NASA’s Chandra X-ray Observatory and the ROSAT telescope (purple), infrared data from NASA’s Spitzer Space Telescope (orange), and optical data from the SuperCosmos Sky Survey (blue) made by the United Kingdom Infrared Telescope.

Located in our galaxy about 5,500 light years from Earth, NGC 6357 is actually a “cluster of clusters,” containing at least three clusters of young stars, including many hot, massive, luminous stars. The X-rays from Chandra and ROSAT reveal hundreds of point sources, which are the young stars in NGC 6357, as well as diffuse X-ray emission from hot gas. There are bubbles, or cavities, that have been created by radiation and material blowing away from the surfaces of massive stars, plus supernova explosions.

Astronomers call NGC 6357 and other objects like it “HII” (pronounced “H-two”) regions. An HII region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms in the surrounding gas to form clouds of ionized hydrogen, which is denoted scientifically as “HII”.

Chandra X-ray Observatory

Researchers use Chandra to study NGC 6357 and similar objects because young stars are bright in X-rays. Also, X-rays can penetrate the shrouds of gas and dust surrounding these infant stars, allowing astronomers to see details of star birth that would be otherwise missed.

A recent paper on Chandra observations of NGC 6357 by Leisa Townsley of Pennsylvania State University appeared in The Astrophysical Journal Supplement Series and is available online. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

Launched in 2013, the trio of Swarm satellites are measuring and untangling the different magnetic fields that stem from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere.

Jet stream in Earth’s core

Together, these signals form the magnetic field that protects us from cosmic radiation and charged particles that stream towards Earth in solar winds.

Measuring the magnetic field is one of the few ways we can look deep inside our planet. As Chris Finlay from the Technical University of Denmark noted, “We know more about the Sun than Earth’s core because the Sun is not hidden from us by 3000 km of rock.”

The field exists because of an ocean of superheated, swirling liquid iron that makes up the outer core. Like a spinning conductor in a bicycle dynamo, this moving iron creates electrical currents, which in turn generate our continuously changing magnetic field.

Tracking changes in the magnetic field can, therefore, tell researchers how the iron in the core moves.

Swarm satellites

The accurate measurements by the unique constellation of Swarm satellites allow the different sources of magnetism to be separated, making the contribution from the core much clearer.

A paper published today in Nature Geoscience describes how Swarm’s measurements have led to the discovery of a jet stream in the core.

Phil Livermore from the University of Leeds in the UK and lead author of the paper said, “Thanks to the mission we have gained new insights into the dynamics of Earth’s core and it’s the first time this jet stream has been seen, and not only that – we also understand why it’s there.”

One feature is a pattern of ‘flux patches’ in the northern hemisphere, mostly under Alaska and Siberia.

Earth’s stormy heart

“These high-latitude flux patches are like bright spots in the magnetic field and they make it easy to see changes in the field,” explained Dr Livermore.

Swarm reveals that these changes are actually a jet stream moving at more than 40 km a year – three times faster than typical outer-core speeds and hundreds of thousands of times faster than Earth’s tectonic plates move.

“We can explain it as acceleration in a band of core fluid circling the pole, like the jet stream in the atmosphere,” said Dr Livermore.

So, what is causing the jet stream and why is it speeding up so quickly?

The jet flows along a boundary between two different regions in the core. When material in the liquid core moves towards this boundary from both sides, the converging liquid is squeezed out sideways, forming the jet.

“Of course, you need a force to move the fluid towards the boundary,” says Prof. Rainer Hollerbach, also from the University of Leeds.

“This could be provided by buoyancy, or perhaps more likely from changes in the magnetic field within the core.”

Swarm: a new constellation in the sky

As for what happens next, the Swarm team is watching and waiting.

Rune Floberghagen, ESA’s Swarm mission manager, added, “Further surprises are likely. The magnetic field is forever changing, and this could even make the jet stream switch direction.

“This feature is one of the first deep-Earth discoveries made possible by Swarm. With the unprecedented resolution now possible, it’s a very exciting time – we simply don’t know what we’ll discover next about our planet.”